Results on AuAu collisions at 130 and 200

Results on Au+Au collisions at 130 and 200 AGe. V from the PHENIX experiment Thomas Peitzmann Westfälische Wilhelms-Universität Münster T. Peitzmann

Outline introduction – motivation – experimental setup – direct photons – single electrons – J/y production global observables: – ET – multiplicity electromagnetic probes conclusions hadron production – identified particles: spectra, mean p. T, d. N/dy – high p. T neutral pion production – particle ratios azimuthal correlations – elliptic flow – jets T. Peitzmann

The Search for the Quark-Gluon-Plasma two phases of strongly interacting matter – ordinary hadronic matter – quark-gluon-plasma » deconfinement » chiral symmetry restoration fundamental understanding of QCD! achievable in – big bang – neutron stars – high energy nuclear reactions T. Peitzmann

Phase Diagram of Strongly Interacting Matter circumstantial evidence for new phase of matter at SPS – dominated by hadronic phase experiments at RHIC (200 Ge. V) – higher energy density and temperature in the initial state – longer lifetime of possible QGP phase – theoretically easier – new observables » jets » heavy quarks T. Peitzmann

QGP Signatures many fascinating hints for new “state of matter” at SPS – – – J/y suppression strangeness enhancement direct photon emission di-electron anomaly. . . opportunities at RHIC – clearer signatures » larger e and T – new domains » hard scattering important » jet quenching as signature jet quenching – parton energy loss in hot, dense matter » medium induced gluon radiation – non-linear (DE L 2) » interference, multiple scattering – sensitive to deconfinement!? – reduced particle yield at high p. T – disappearance of jet structures T. Peitzmann

T. Peitzmann

The PHENIX Experiment PHENIX = Pioneering High Energy Nuclear Interaction e. Xperiment study of nuclear matter under extreme conditions (quark-gluonplasma) – focus on penetrating probes (g, e+e-, m+m-) » sensitive to early phase – identified hadrons at high p. T – global variables, flow, interferometry, fluctuations, . . . – nuclear reactions at the highest available beam energies » Au+Au at 200 AGe. V a multitude of observables future: measurement of the spin structure of the proton – polarized proton beams – e. g. measurement of the polarized gluon structure functions » quark-gluon-Compton-scattering T. Peitzmann

Experimental Setup two central detector arms – charged particle tracking and PID – EM calorimetry two muon arms – muon tracking and ID global detectors (trigger, centrality, vertex) » Beam-Counter » Zero-Degree-Calorimeter T. Peitzmann

PHENIX – Run II Au-Au at Ecm = 200 Ge. V – RHIC delivered 42 mb-1 to PHENIX – “minimum bias” and Level-2 triggers: 24 mb-1 Proton-Proton at Ecm = 200 Ge. V – RHIC delivered 700 nb-1 to PHENIX – “minimum bias” and Level-1 triggers 150 nb-1 T. Peitzmann

Excellent Particle Identification Hadron ID in TOF Electron ID in RICH and EMCal All charged tracks Apply RICH cut Real Net signal Background EMC energy / Momentum T. Peitzmann

Global Variables charged multiplicity and transverse energy significantly higher at RHIC compared to SPS weak centrality dependence of Nch/Npart and ET/Npart energy density in 2% most central collisions T. Peitzmann

Nch Model Comparison HIJING X. N. Wang and M. Gyulassy, PRL 86, 3498 (2001) EKRT K. J. Eskola et al, Nucl Phys. B 570, 379 and Phys. Lett. B 497, 39 (2001) KLN D. Kharzeev and M. Nardi, Phys. Lett. B 503, 121 (2001) D. Kharzeev and E. Levin, Phys. Lett. B 523, 79 (2001) Mini-jet S. Li and X. N. Wang Phys. Lett. B 527: 85 -91 (2002) T. Peitzmann

Identified Charged Hadron Spectra PHENIX Preliminary identified hadrons over large p. T-range protons ≈ pions at 2 Ge. V/c T. Peitzmann

Mean Transverse Momentum open symbols : 130 Ge. V data increase for peripheral collisions and saturation for central values and increase larger for heavier particles – collective transverse flow? T. Peitzmann

Pseudorapidity Density open symbols: 130 Ge. V data p+ p+ K+ K- p Positive weak centrality dependence of (NX/dy)/Npart behavior similar for 130 and 200 Ge. V pbar Negative T. Peitzmann

Suppression of Hadron Production M. M. Aggarwal et al. , Eur. Phys. J. C 23, 225 -236, 2002 K. Adcox et al. , Phys. Rev. Lett. 88, 22301 (2002) ratio of p. T-spectra – AA central / pp RAA =1 for scaling with number of binary collisions RAA < 1 for central Au+Au reactions at RHIC (130 AGe. V) RAA > 1 for reactions at SPS and ISR T. Peitzmann

The Reference: Spectra in pp at 200 Ge. V measurement of neutral pion spectra in pp – reference for AA » same detector, same systematics as AA consistent with p. QCD calculations T. Peitzmann

Neutral Pion Spectra in Au+Au at 200 Ge. V T. Peitzmann

Suppression in Hadron Spectra – The Nuclear Modification Factor nuclear modification factor – p. T-spectra for AA-central/pp strong suppression in p 0: – decreasing with p. T – factor 6 at p. T = 6 -8 Ge. V/c similar suppression in charged hadrons – RAA slightly higher at intermediate p. T? T. Peitzmann

High p. T Neutral Pion Suppression – Comparison To Theory p. QCD calculations: – P. Levai, Nucl. Phys. A 698 (2002) 631 – X. N. Wang, Phys. Rev. C 61 (200) 064910 – I. Vitev, talk at QM 2002 so far suppression not described by theories – calculations without energy loss completely off – energy loss calculations show different p. T dependence T. Peitzmann

Centrality Dependence of Suppression RAA for neutral pions as a function of centrality – gradual decrease – stronger decrease for higher p. T no threshold effect – surface-to-volume? » high p. T particle emission only from surface? T. Peitzmann

Chemical Composition at High p. T p/p and p/p ratios ≈1 for p. T = 3 Ge. V/c in central collisions p/p ratio decreasing at high p. T? – also in central collisions? T. Peitzmann

Chemical Composition at High p. T ratio p/h ≈ 0. 5 in min. bias – similar in central reactions important baryon and/or kaon contribution out to p. T = 9 Ge. V/c? – different from p. QCD expectations? T. Peitzmann

Elliptic Flow in Minimum Bias Au+Au at 200 AGe. V azimuthal asymmetry in particle emission PHENIX preliminary – strong effect due to pressure gradient (hydrodynamic flow) flow saturates for p. T > 3 Ge. V/c – asymmetry in hard scattered particles – asymmetric jet quenching? T. Peitzmann

Jet Evidence in Azimuthal Correlations at RHIC correlation of charged tracks with g (p 0) in triggered events – trigger particle p. T > 2. 5 Ge. V/c – Df distribution for p. T = 2 -4 Ge. V/c signature of jets in Au+Au – consistent with PYTHIA calculations and p+p data similar correlations between pairs of charged particles fit of jet signal with Gaussian – width decreases as a function of p. T – transverse momentum relative to jet axis consistent with expectation for jet fragmentation T. Peitzmann

Photon Measurements direct photon analysis in PHENIX – search for thermal photons – prompt photons as “calibration” for high p. T hadron production PHENIX preliminary no significant excess over hadron decays observed – promising results – important: redundancy of PHENIX » photon measurements in two different EMCal detectors and via conversion » two calorimeters yield c onsistent results » conversion method under study – significantly reduced systematic errors in the future PHENIX preliminary T. Peitzmann

Single Electron Spectra electron measurements in PHENIX – tracking in Drift- and Pad. Chambers – identification in RICH and EMcalorimeter yield and spectral shape consistent with PYTHIA calculation scaling with binary collisions – little energy loss? subtraction of background – photon conversions from mesons and p 0 -Dalitz dominant » pions measured in the same experiment! » identification of photonic sources by converter method physics signal? – main source: open charm? T. Peitzmann

J/y in p+p Collisions J/y �+ �- J/y m+ m - T. Peitzmann

J/y Cross Section in p+p Collisions rapidity distribution energy dependence of total cross section T. Peitzmann

J/y in Au+Au Collisions centrality dependence – normalized to binary collisions T. Peitzmann

Summary quenching of high p. T hadrons in central reactions established – neutral pions suppressed by 1/6 up to p. T = 8 Ge. V/c – suppression continuous in centrality (no threshold) – decreasing <p. T> at high p. T for charged hadrons chemical composition not (yet) jet-like – only ≈50% of hadrons are pions – role of baryons at high p. T (p/p, p/p)? saturation of v 2 for p. T > 3 Ge. V/c – hydrodynamics important for p. T < 3 Ge. V/c? – amount of v 2 from partial quenching? jets re-discovered in AA at RHIC – near-side correlation with trigger photon – most trigger particles (decay gamma) for p. T > 2. 5 Ge. V/c from jets? ! T. Peitzmann

Summary 2 promising first results for electromagnetic probes – direct photon analysis under way – single electrons consistent with charm predictions from p. QCD – J/y cross section measured in p+p – J/y measured in Au+Au – eagerly waiting for higher luminosity many more results from hadrons and global observables – – – multiplicity transverse energy identified hadrons elliptic flow not discussed: » » interferometry fluctuations production of L and deuterons. . . T. Peitzmann

Energy Dependence of p. T-spectra in pp and AA spectra in pp K. Reygers et al. , Hirschegg 2002 – strong variation with beam energy – “flattening” of spectra – power law » influence of hard scattering spectra in AA – little variation with beam energy – almost exponential » influence of thermal production? T. Peitzmann

Interlude: Thermalization and Hadron Spectra spectra of pions and (anti)protons description by hydrodynamical source T. P. , nucl-th/ 0207012 – perfect description possible Tch = 172 ± 2 Me. V m. B = 37 ± 4 Me. V Tkin = 123 ± 6 Me. V < b. T > = 0. 45 ± 0. 02 doesn’t explain suppression – need stronger suppression to account for additional hydrodynamic production T. Peitzmann

New Results at 200 Ge. V identified particles are best! PHENIX neutral pions at high p. T identified charged particles to come? T. Peitzmann

Centrality Selection ZDC vs BBC Define centrality classes: ZDC vs BBC ET b Nch EZDC QBBC Extract N participants: Glauber model PHENIX preliminary Nch PHENIX preliminary ET T. Peitzmann